Al Gietzen wrote:

BTW; I don't think I ever posted here the very sparse data I got on fuel
consumption.  A total of 4 data points.

FUEL CONSUMPTION

The fuel consumption data was very limited because of a high degree of
scatter caused by poor flow meter performance.  The computer logged data
for this parameter was essentially unusable.  Some good data was
measured by doing timed runs, i.e.; set up a steady state engine
operation and take weight readings of a fuel supply container at one
minute intervals for five or more minutes.  The number of these runs was
limited to 4 as these were the last tests we were doing and ran out of
time.  The results are as follows:

 WOT

RPM       Mixture   MAP ("Hg) Avg EGT (F)   HP     BSFC    mpg

5,100     Max pow    26.6      1,570       220     0.52    12.5

5,100     Leaned     23.8      1,556       155     0.49    16.9

5,000     Max pow    24.8      1,544       200     0.54    12.9

4,550     Max pow    21.8      1,488       150     0.55    15.6

The max power mixture setting was approximate, and was typically with a
lambda of about 0.94, and maybe 100 - 150 degrees rich of peak EGT.  The
"leaned" run was done at about the same amount lean of peak.  The leaned
run may have no relevance in actual operation with a prop because rpm
was held as mixture was reduced by varying load while trying to maintain
about 24" MAP. Power dropped significantly, but estimated fuel economy
is clearly improved.

The miles/gal values were computed using the Velocity factory values of
airspeed as a reference and adjusting it by the cube root of HP.

Al, At what altitude and temperature was the dyno? It appears you are losing
MAP/power because of the air cleaner and or a pressure drop across the butterfly
valves.

Paul Lamar
 
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